Conventionally widely known are transfer systems that include a local clean device referred to as an equipment front end module (EFEM) and that carry a substrate, such as a wafer, in and out of a processing device in a semiconductor manufacturing process from and to a space formed in the EFEM.
Transfer systems typically include an arm body. Such transfer systems transfer a substrate by moving the arm body in a horizontal direction with the substrate placed and held on the arm body or an end effector provided to the tip of the arm body, for example.
In each processing in the semiconductor manufacturing process, such as washing processing, deposition processing, and photolithography processing, a substrate may be exposed to an environment of high heating, supercooling, and the like, and the substrate is often at abnormal temperature after the processing.
To address this, Japanese Patent Application Laid-open No. 2002-343847, for example, discloses a wafer transfer apparatus that includes two arm bodies arranged in two tiers and that uses an upper arm body only for a substrate at high temperature after the processing and uses a lower arm body only for a substrate at normal temperature before the processing.
In the conventional transfer system, however, the temperature of the substrate after the processing may possibly affect the substrate before the processing. The state of the substrate at abnormal temperature includes a state at low temperature besides a state at high temperature, for example. If such a substrate at low temperature is placed on the upper arm body, cold air descends because of heat convection. As a result, the substrate is highly likely to affect a substrate at normal temperature placed on the lower arm body.
To address this, the two arm bodies may be used in an opposite manner to the case where the substrate after the processing is at high temperature. However, to transfer another substrate at high temperature, the two arm bodies need to be used in a further opposite manner, thereby making the processing complicated.
Furthermore, in the EFEM described above, a downflow device often creates downflow of clean air because of the need to maintain the space with an extremely clean air. In this case, the heat convection is made complicated, thereby making it difficult for the conventional transfer system to deal with the circumstances.